In some agricultural areas it is popular to cut and windrow, or swath, crops before harvesting in order to promote earlier and more uniform maturing and to achieve the necessary drying of the crop. An implement known as a swather comprises generally a cutting header and belts to lay cut crop in a swath. The header is typically raised and lowered by lift hydraulic cylinders to follow ground contours and variations in crop height. Such swathers can be self-propelled, or towed behind a tractor.
There is risk of loss or damage to a crop while it is in the swath. In the case of light and fragile crops such as canola, peas, flax or beans this risk includes loss of crop that is shelled out onto the ground due to wind action on the swath and the possibility of the wind actually dislocating and scattering the swath, making efficient harvesting impossible.
As these crops dry in the swath they become lighter, more brittle and increasingly susceptible to movement & damage by the wind. To minimize losses and damage to the crop in the swath it has become common practice to use a swath roller to compact the swath and push it down into the supporting standing stubble and anchor the swath to resist movement by wind.
Swath rollers are typically mounted onto a swather, or mounted in a frame on wheels that is towed along behind the swather. Swath rollers generally comprise a drum of substantially cylindrical shape that is mounted either in a wheeled frame that straddles the swath, or in a frame attached to a swather such that the drum is positioned over the swath and rolls along the top of the swath that has just exited the swather and pushes the swath down into the standing stubble of the cut crop.
Simple cylindrical swath rollers do nothing to compact or anchor the edges of the swath and so drums have been developed with ends which are shaped generally as the frustum of a cone so that the roller contacts both the top and edges of the swath, and pushes the edges of the swath down farther into the standing stubble than the middle. The swath is then more resistant to movement by wind. Bumps and the like can also be provided on the ends of the drum in an attempt to knit the swath into the standing stubble. These various drum end sections can be generally referred to as edge compacting ends.
Canadian Patent Number 2,311,694 to Cresswell illustrates a typical swath roller of both the tow behind trailer and swather mounted types. In swath rollers where the drum is mounted on a trailer pulled behind the swather, the vertical position of the drum with respect to the frame is typically adjustable, but once adjusted the vertical position is fixed during operation, and the machine must be stopped for the operator to attend to further adjustments. The trailers used typically comprise a light frame with a wheel on each side, and the drum mounted between the wheels such that the rotational axes of the wheels and drum are substantially aligned. The height of the drum above the ground then stays substantially the same as the swather moves along sloping terrain.
On typical swather mounted models, the drum is mounted in a frame that is pivotally attached to the rear of the swather about a horizontal axis oriented perpendicular to the travel direction. A winch is typically mounted on the swather and a cable to the frame holds the frame and drum off the ground at the desired vertical location, low enough to push the swath into the stubble, but above the ground. The drum and frame can float up from this minimum vertical location, but the winch cable prevents it from moving down past the limit of the cable.
As the swather moves through a field, the volume of crop material being cut can vary significantly, such that the size of swath exiting the rear of the swather varies significantly as well, and in heavy crop areas the height of the standing stubble left is often significantly higher as well Where the swath gets very large and the stubble gets high, the drum floats upward. On trailer mounted drums, the wheels of the light trailer can be lifted off the ground, while on swather mounted drums the drum simply floats up and down as the swath varies.
In a typical operation the height of the drum is set at a height above the ground that is suitable for the average crop volume. In heavier crop areas the drum then floats upward, while in lighter crop areas, where the stubble is typically shorter, the drum may have little contact with the swath.
Canadian Patent Number 2,635,859 to Miller discloses a swath roller system where the drum is moved up and down by an actuator that can be activated by the swather operator to move the drum up and down with respect to the ground while the vehicle is moving along the ground. While the drum does move up and down with respect to the ground, this is accomplished by moving the drum up and down with respect to the vehicle, either a swather or trailer, to which same is mounted, and the drum is at a fixed location with respect to the swather or trailer. Unless the drum is mounted on the same rotational axis as wheels of the vehicle, the relative position of the drum and the ground can change significantly when traversing steep slope changes, such that the drum can sometimes be above and not touching the swath, or can be squashing the swath into the ground. To avoid such problems in varying terrain, the drum may be operated in a float position so that the drum moves up and down in response to changes in the swath or the terrain being traveled.
When operated in the float position the drum exerts a downward anchoring force on the swath that is equal to the weight of the drum and any mounting brackets etc. which move up and down with the drum.